1. Field of the Invention
The present invention relates to a movement direction control apparatus and a computer program enabling even a monocycle to freely veer in a yaw direction.
2. Description of the Related Art
Conventionally, when a monocycle moves, a body swings in a rotation direction with a substantial front-back direction defining an axis (hereinafter, referred to as a roll direction), and in a rotation direction with a substantial right-left direction defining an axis (hereinafter, referred to as a pitch direction), and thus, movements need to be controlled so as to move or stop the body without falling by controlling balance in the roll direction and in the pitch direction. In order to control the balance in the roll direction and in the pitch direction, an inclination of the body needs to be properly detected, and for example, a method of detecting an angular velocity, using an angular velocity sensor and integrating the detected angular velocity to thereby estimate the inclination of the body has been employed (refer to WO2007/063665).
Moreover, the monocycle cannot easily veer by changing an angle of a front wheel as in a two-wheeler, and for example, in many cases, by swinging the body in the roll direction and in the pitch direction, the body is rotated in a rotation direction with a substantially vertical direction of the body defining an axis (hereinafter, referred to as a yaw direction) to change a traveling direction. That is, as disclosed in “Attitude Control of Monocycle” by Takashi Kasai, Master's Thesis in Graduate School of Systems and Information Engineering, University of Tsukuba, January 2005, p. 1-37, by applying sine wave inputs in the roll direction and in the pitch direction to fluctuate phases of both the applied sinewave inputs, a yaw angle change amount is varied, and a yaw angle of a wheel is feedback-controlled so as to perform the veering in a desired movement direction.
However, while in the monocycle disclosed in “Attitude Control of Monocycle” by Takashi Kasai, Master's Thesis in Graduate School of Systems and Information Engineering, University of Tsukuba, January 2005, p. 1-37, the inclination of the body with respect to a gravity direction (vertical direction) is detected by an acceleration sensor, the vertical direction is not necessarily in a balanced state in the roll direction and in the pitch direction. Thus, there is a problem in that when the vertical direction is not in the balanced state, correction for the balanced state is disabled. Also, there is a problem in that a plurality of acceleration sensors are required in addition to a gyrosensor to estimate the inclination of the body, which makes simplification and downsizing of the apparatus difficult.
Moreover, in a two-wheeler, by controlling operation of an actuator that causes a steerable front wheel provided in a front portion of the body to be steered, the veering in a desired movement direction is enabled. However, in a monocycle, there is a problem in that since a steering wheel and a drive wheel are defined by the same wheel and a friction coefficient differs greatly at a time period between during movement and during stopping, it is difficult to specify a rotation moment to be applied to a desired rotation angle.